When IK bone moved wrong part of mesh deforms
Yes, I checked the file, there are still subtle weight painting errors... I know they're subtle because it's difficult to see because they are just drawn in a slightly lighter blue colour, and some weighted vertex somewhat hidden into the folds of the suit of the character. but trust me, that is the problem. I can show you where they are some, in an image:



I removed all of them from the right IK arm, and now it moves just the supposed geometry. 

There is a way to help you spot those subtle areas, and you can use it temporarily just to fix your weights: in the user preferences, activate the "custom weight paint range", and setup one that will help you, like did here:



Here I setup 2 control points in the colorramp: 


the first is at 0 exactly (vertices with zero weight): black
the second, at 0.002, white (vertices with weight 0.002)


you cannot even see the black (zero) point, because it's very, very near to the white, but it's there.

in this way it's very easy to see where the bad paints are... when finished, just disable this feature, and get back to the default rainbow scheme...